1. JDBC – Java DataBase Connectivity
Information Management
JDBC – Java DataBase Connectivity

2. What is JDBC?
“An API that lets you access virtually any tabular data source from the Java programming language”
JDBC Data Access API – JDBC Technology Homepage
What’s an API?
See J2SE documentation
What’s a tabular data source?
“… access virtually any data source, from relational databases to spreadsheets and flat files.”
JDBC Documentation
We’ll focus on accessing Oracle databases

3. General Architecture
What design pattern is implied in this architecture?
What does it buy for us?
Why is this architecture also multi-tiered?

5. Basic steps to use a database in Java
1.Establish a connection
2.Create JDBC Statements
3.Execute SQL Statements
4.GET ResultSet
5.Close connections

6. 1. Establish a connection
import java.sql.*;
Load the vendor specific driver
Class.forName("oracle.jdbc.driver.OracleDriver");
What do you think this statement does, and how?
Dynamically loads a driver class, for Oracle database
Make the connection
Connection con = DriverManager.getConnection( username, passwd);
What do you think this statement does?
Establishes connection to database by obtaining a Connection object

7. 2. Create JDBC statement(s)
Statement stmt = con.createStatement() ;
Creates a Statement object for sending SQL statements to the database

8. Executing SQL Statements
String createLehigh = "Create table Lehigh " +
"(SSN Integer not null, Name VARCHAR(32), " + "Marks Integer)";
stmt.executeUpdate(createLehigh);
//What does this statement do?
String insertLehigh = "Insert into Lehigh values“ + "( ,abc,100)";
stmt.executeUpdate(insertLehigh);

9. Get ResultSet String queryLehigh = "select * from Lehigh";
ResultSet rs = Stmt.executeQuery(queryLehigh);
//What does this statement do?
while (rs.next()) {
int ssn = rs.getInt("SSN");
String name = rs.getString("NAME");
int marks = rs.getInt("MARKS"); }

10. Close connection
stmt.close();
con.close();

11. Transactions and JDBC
JDBC allows SQL statements to be grouped together into a single transaction
Transaction control is performed by the Connection object, default mode is auto-commit, I.e., each sql statement is treated as a transaction
We can turn off the auto-commit mode with con.setAutoCommit(false);
And turn it back on with con.setAutoCommit(true);
Once auto-commit is off, no SQL statement will be committed until an explicit is invoked con.commit();
At this point all changes done by the SQL statements will be made permanent in the database.

12. Handling Errors with Exceptions
Programs should recover and leave the database in a consistent state.
If a statement in the try block throws an exception or warning, it can be caught in one of the corresponding catch statements
How might a finally {…} block be helpful here?
E.g., you could rollback your transaction in a catch { …} block or close database connection and free database related resources in finally {…} block

13. Another way to access database (JDBC-ODBC)
What’s a bit different
about this architecture?
Why add yet
another layer?

14. Sample program import java.sql.*; class Test {
public static void main(String[] args) {
try {
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); //dynamic loading of driver
String filename = "c:/db1.mdb"; //Location of an Access database
String database = "jdbc:odbc:Driver={Microsoft Access Driver (*.mdb)};DBQ=";
database+= filename.trim() + ";DriverID=22;READONLY=true}"; //add on to end
Connection con = DriverManager.getConnection( database ,"","");
Statement s = con.createStatement();
s.execute("create table TEST12345 ( firstcolumn integer )");
s.execute("insert into TEST12345 values(1)");
s.execute("select firstcolumn from TEST12345");

15. Sample program(cont) ResultSet rs = s.getResultSet();
if (rs != null) // if rs == null, then there is no ResultSet to view
while ( rs.next() ) // this will step through our data row-by-row
{ /* the next line will get the first column in our current row's ResultSet
as a String ( getString( columnNumber) ) and output it to the screen */
System.out.println("Data from column_name: " + rs.getString(1) ); }
s.close(); // close Statement to let the database know we're done with it
con.close(); //close connection
catch (Exception err) { System.out.println("ERROR: " + err); }

16. Mapping types JDBC - Java

17. JDBC 2 – Scrollable Result Set…
Statement stmt =
con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY);
String query = “select students from class where type=‘not sleeping’ “;
ResultSet rs = stmt.executeQuery( query );
rs.previous(); / / go back in the RS (not possible in JDBC 1…)
rs.relative(-5); / / go 5 records back
rs.relative(7); / / go 7 records forward
rs.absolute(100); / / go to 100th record

18. JDBC 2 – Updateable ResultSet…
Statement stmt =
con.createStatement(ResultSet.TYPE_FORWARD_ONLY,
ResultSet.CONCUR_UPDATABLE);
String query = " select students, grade from class
where type=‘really listening this presentation’ “;
ResultSet rs = stmt.executeQuery( query );
while ( rs.next() ) {
int grade = rs.getInt(“grade”);
rs.updateInt(“grade”, grade+10);
rs.updateRow(); }

19. Metadata from DB
A Connection's database is able to provide schema information describing its tables, its supported SQL grammar, its stored procedures the capabilities of this connection, and so on
What is a stored procedure?
Group of SQL statements that form a logical unit and perform a particular task
This information is made available through a DatabaseMetaData object.

20. Metadata from DB - example…
Connection con = …. ;
DatabaseMetaData dbmd = con.getMetaData();
String catalog = null;
String schema = null;
String table = “sys%”;
String[ ] types = null;
ResultSet rs =
dbmd.getTables(catalog , schema , table , types );

21. JDBC – Metadata from RS
public static void printRS(ResultSet rs) throws SQLException {
ResultSetMetaData md = rs.getMetaData();
// get number of columns
int nCols = md.getColumnCount();
// print column names
for(int i=1; i < nCols; ++i)
System.out.print( md.getColumnName( i)+",");
/ / output resultset
while ( rs.next() )
{ for(int i=1; i < nCols; ++i)
System.out.print( rs.getString( i)+",");
System.out.println( rs.getString(nCols) ); }

22. JDBC and beyond (JNDI) Java Naming and Directory Interface
API for network-wide sharing of information about users, machines, networks, services, and applications
Preserves Java’s object model
(JDO) Java Data Object
Models persistence of objects, using RDBMS as repository
Save, load objects from RDBMS
(SQLJ) Embedded SQL in Java
Standardized and optimized by Sybase, Oracle and IBM
Java extended with directives: # sql
SQL routines can invoke Java methods
Maps SQL types to Java classes

23. JDBC Drivers Java application JDBC- Driver manager Native
Protocol driver
Net-driver
API-driver
JDBC-ODBC
bridge
Client library
DB-
Middleware
ODBC
JDBC-API

24. JDBC references JDBC Data Access API – JDBC Technology Homepage
JDBC Database Access – The Java Tutorial
JDBC Documentation
java.sql package
JDBC Technology Guide: Getting Started
JDBC API Tutorial and Reference (book)

25. JDBC JDBC Data Access API – JDBC Technology Homepage
JDBC Database Access – The Java Tutorial
JDBC Documentation
java.sql package
JDBC Technology Guide: Getting Started
JDBC API Tutorial and Reference (book)